New material of Argochampsa krebsi (Crocodylia: Gavialoidea) from the Lower Paleocene of the Oulad Abdoun Basin (Morocco):: phylogenetic implications

New material from the Lower Paleocene of the Oulad Abdoun Basin, Morocco, including postcranial material permits a new description of Argochampsa krebsi. The odontoid process of the axis bears a strong lateral apophysis, continuous on the anterolateral margin of the centrum. This process has never been observed such developed in other crocodylians. The single preserved posterior cervical vertebra exhibits a particularly short neural spine, much shorter than that is observed in Alligator mississippiensis, Crocodylus porosus, and Gavialis gangeticus. A phylogenetic analysis, including new coding of A. krebsi, provide a result that is globally congruent with previous works, but differs significantly in the relationships of the gavialoids. A. krebsi is more closely related to G. gangeticus than is Eogavialis africanum. The South American Ikanogavialis gameroi and Gryposuchus colombianus form a polytomy, and are more closely related to G. gangeticus than is Piscogavialis jugaliper-foratus, a gavialoid from Peru. The South American gavialoids may thus not be monophyletic. This result may indicate, contrary to previous result, a more complex paleobiogeographic history. Thus, a multiple invasion of South America by gavialoids from Africa is equally parsimonious with a single invasion, and an invasion from South American to Asia is equally parsimonious with an invasion froth Africa. (c) 2006 Elsevier Masson SAS. All rights reserved.